Flashcards in Gap junctions/Electrical Synapses Deck (43):
What are gap junctions?
An array of intercellular channels for direct cell-to-cell communication.
What are gap junctions composed of?
What type of current is used for cell-to-cell communication?
What leads to complex assemblies of subunits of gap junctions made?
Co-expression of connexins.
How are intercellular channels at gap junctions packaged?
What direction is signalling between cells using gap junctions?
Give two examples were gap junctions are used?
Oocyte and granulosa cells.
Epithelial cells of the gut.
What organ are gap junctions found in?
They are ubiquitous (found everywhere)
Found throughout the body.
What happens if there is a change in connexin protein or genes?
Causes connexin-associated disease.
Many of these as GJ are important throughout the body.
What is the permeability of gap junctions?
They are permeable to:
inorganic ions (K, Na, Cl, HCO3)
Small organic (signalling) molecules (cAMP, IP3)
Describe the bystander effect that is mediated by the connexin?
When looking at tumorigenesis.
When intoxicating a cell with pro-drug it only kills that one cell while if gap junctions were used it kills off all bystander cells that has the toxic gene.
What is the synaptic transmission mediated by?
How many connexin genes are there?
20 different connexin genes
Where are the connexin genes expressed? and by what type of cell?
Half are expressed in the brain.
Most by glia cells.
What is the most important protein when looking at electrical synapses?
Name the two types of synapse transmission?
What is the difference between chemical and electrical synapse?
Chemical: using a transmitter (no direct contact)
Electrical: without transmitter (direct contact to transfer tonic current)
Assaying function of electrical synapses?
Specificity between different types.
Once applied cannot be reused
Name the 3 characteristics of electrical synaptic transmission?
Can pass sub threshold current
Strongly postsynaptic responses
What is required for electrical transmission?
Time difference between electrical and chemical transmission?
Electrical activate faster than chemical ones.
Direction of release between electrical and chemical transmission?
Electrical almost always bidirectional.
Polarisation specificity between electrical and chemical transmission?
Chemical are de/hyperpolarising.
Electrical not specificity.
Reliability between electrical and chemical transmission?
Electrical are reliable.
Chemical reliability varies.
Metabolically expenditure between electrical and chemical transmission?
Chemical uses more energy than electrical.
How would you test the electrical synapses?
Use gap junctions to look at the fast transmission between neurones.
Knockout the specific gene
How would you test the chemical synapses?
Look at the morphology and protein associated with vesicle docking and release.
Name the 6 properties that are important when looking at synapses?
2. Shorter synaptic delay.
3. Sign preservation.
4. Mediated both hyper polarising and depolarising responses.
5. Facilitates synchrony and promotes AP.
6. Coordinates activity in cell-to-cell fashion.
What kind of network is created by electrical synapses?
Synchronously coactive neurones.
What does Cx36 do?
Creates multiple groups of coupled interneurones.
Restricted to interneurones.
Couples similar subtypes.
Creates homocellular assemblies.
Name the two different expression of connexins?
Cx36 is vital for generating?
Synchrony generates brain rhythms
What are electrical synapse vital for in the cerebellum?
Important in neural circuits.
How are the inferior olivary nucleus important in motor impairment?
Neurones in this area generate sub threshold rhythms
Which occasionally trigger APs.
Send signals to the cerebellum.
How are the Cx36 linked to the inferior olivary nucleus that is necessary for motor impairment?
The membrane rhythms in neurones of the olive are synchronised.
Requires electrical synapses. Thus requires Cx36
When muscle contractions are impaired.
What protein is most electrical synapses comprised of?
What other things play a role in comprising the electrical synapses?
Other connexins and pannexins.
What are the electrical synapses in the retina comprised of?
What passes through the electrical synapses?
Usually allows ionic current and small organic molecules.
What is the role of the electrical and chemical synapses?
Together generate complex electrical activity that encodes brain function.